In what police are describing as ‘vile’ and ‘horrendous’, the two befriended and groomed boys as young as 13 online who were gay, bi or questioning.

Some of their victims had only just come out as gay and many lost their virginity to the men, according to the detective in charge of the case.

The sex was usually unprotected and March, who has HIV, did not tell the teens about his status.

Detective Inspector Delphine Waring, from South Yorkshire police, said while the men did not lie about their ages, they knew most of their victims were underage and vulnerable.

As reported by Sky News, she described their crimes as ‘absolutely despicable’.

‘They've preyed on vulnerable young boys who have every right, in this day and age, to be able to experiment and use the internet,’ she said.

‘Many of these children were confused about their sexuality or were vulnerable in other ways – some had only just come out at school and were being bullied when they were preyed upon by these men,’ Waring said, as reported by The Guardian.

‘Initially quite a few of the boys did not see themselves as victims because they had willingly gone to meet Marsh or Davis and there was no coercion or force used in most cases.’

Marsh, who also used the names Tony Taylor and Tony Smith, pleaded guilty to 34 offences including possessing and distributing indecent images of children and sexual activity with a child.

As he worked as a travelling salesman, he met his victims in hotels across the country.

Davis, who also used the name James Parkin, admitted 21 offences including raping a 13-year-old, sexual activity with a child and taking indecent photographs of a child.

A large number of his victims were abused at his house.

The two men, who had never met but were friends online, admitted to sharing the contact details of their victims.

Both have also pleaded guilty to one joint charge of conspiring to commit sexual activity with children.

The offences to which they plead guilty date back to as far as 2005 and involved 10 teen boys aged between 13 and 17.

The men have denied further 14 offences at a court hearing on 27 September. In Davis's case, he claims he thought some of the boys were over 16.

Police have since identified 10 more victims, although Waring believes there could be ‘dozens more’.

All identified victims have received help and support from police and health professionals.